1. Field of the Invention
This invention relates to a carrier for holding and moving test sample devices through an automated sample testing instrument. The test sample devices are used for testing biological, microbiological, chemical or other types of samples.
2. Description of Related Art
Biological and other types of samples can be reacted and subjected to chemical or optical analysis using various techniques, including transmittance and/or fluorescence optical analysis. The purpose of the analysis may be to identify an unknown biological agent or target in the sample, to determine the concentration of a substance in the sample, or determine whether the biological agent is susceptible to certain antibiotics, as well as the concentration of antibiotics that would be effective in treating an infection caused by the agent.
In the mid-to late 1970's, engineers and scientists working with the applicants' assignee and its predecessor in interest developed a technique for conducting optical analysis of biological samples using a sealed test sample card containing a plurality of small sample wells. The technique, and related instruments and devices, came to be known in the industry as the “Vitek® System”. The Vitek® System was (and continues to be) a commercial success.
The cards used in the Vitek® System are known in the patent literature, see e.g., U.S. Pat. Nos. 4,118,280, 3,963,355, 4,018,65; 4,116,775 and 4,038,151. More recent versions of the cards are described in U.S. Pat. Des. Nos. 382,647, Des. 414,272, 5,609,828, 5,746,980, 5,766,553, 5,843,380, 5,869,005, 5,916,812, 5,932,177, 5,951,952, and 6,045,758.
Cards were developed for both identification of unknown microorganisms that may be present in a sample and susceptibility of a known organism to precisely calibrated concentrations of antibiotics. During manufacture of the cards, the wells are filled with either various types of growth media for various biological agents, or else concentrations of different antibiotics, and covered with a transparent sealing tape.
The cards have an external transfer tube port as a mechanism for allowing a fluid sample to enter the card. The cards further include an internal fluid passageway structure for allowing fluid to enter the wells of the card from the transfer tube port. One end of straw-like transfer tube is inserted into the transfer tube port. The other end is inserted into an open receptacle (e.g., test tube) containing the fluid sample to be tested. In accordance with the teaching of the prior art Charles et al. patent, U.S. Pat. No. 4,188,280, the card with attached transfer tube and test tube are placed into a stand-alone vacuum and filling sealing machine, known as the Vitek® Filler Sealer. The filling and sealing machine generates a vacuum. When the vacuum is released, the fluid sample is drawn from the test tube into the transfer tube and through the internal channels of the card and into all of the sample wells. In the instrument of the prior art Charles et al. '280 patent, after the wells of the card are loaded with the sample, the cards are manually inserted into a slot in a sealer module in the machine, where the transfer tube is cut and melted, sealing the interior of the card.
The cards are then manually removed from the filler/sealer module and loaded into a reading and incubating machine, known as the Vitek® Reader, also described in the Charles et al. '280 patent. The reading and incubating machine incubates the cards at a desired temperature. An optical reader is provided for conducting transmittance testing of the wells of the card. Basically, the cards are stacked in columns in the reading machine, and an optical system moves up and down the column of cards, pulling the cards into the transmittance optics one at a time, reading the cards, and placing the cards back in the column of cards.
The arrangement of the early Vitek System (as described in the Charles et al. '280 patent) has several limitations, in that two machines, a filler/sealer and a reader, are required to process and analyze the cards. Furthermore, additional time and labor are required to conduct the complete analysis of the card. The applicants' assignee later developed and commercialized a fully automated instrument, referred to herein and known in the art as the “Vitek 2” instrument. The Vitek 2 instrument automates both the vacuum loading and sealing operations and combined them with incubation and reading in a single instrument. The overall instrument is described in several patents, including U.S. Pat. Nos. 5,762,873 and 6,086,824, the contents of which are incorporated by reference herein.
Briefly, the “Vitek 2” system provides an automated sample testing machine that performs dilutions for susceptibility testing, fills the cards with the samples at a vacuum station, and seals the card by cutting the transfer tube, and conducts incubation and optical transmittance and fluorescence analysis of the cards, all automatically. The machine provides for novel pipetting and diluting stations, permitting fluids to be added to the test tubes or transferred from one test tube to another. The machine is capable of conducting simultaneous susceptibility and identification testing of a sample placed in a single test tube. The machine provides for rapid, automatic identification and susceptibility testing of the sample.
The instrument uses a sample tray or “boat” and a test sample positioning or transportation system that moves the “boat” in four separate paths around a rectangular base pan among the various stations. The user places a cassette or carrier loaded with cards and test tubes containing samples into the boat at a loading station. The design of the positioning system includes a motor driven paddle or arm that engages with the side of the boat and pulls it along one of the four paths. The test sample positioning system and the carrier of the Vitek 2 instrument is described in U.S. Pat. Nos. 5,736,102, 5,762,874, 5,798,182, 5,798,084, 5,853,667, and 5,897,835.
The present invention provides improvements to the cassette or carrier of the type described in the above-referenced patents. A primary advantage of the present carrier is that it provides built-in positioning features that allow the position of the carrier, and test sample devices held therein, to be precisely determined though the use of fixed optical interrupt sensors placed along the path of carrier travel in the instrument.
While this background discussion has set forth the context of the invention in relation to the closest known prior art, the various aspects and features of the inventive carrier are applicable to other types of sample testing and processing systems that are known in the art now or may later be developed. Thus, the inventors do not limit the scope of the invention to any particular sample testing device format, instrument or testing protocol. Moreover, the features of the present carrier are applicable to other types of testing and other instrument architectures besides biological sample testing and the particular instrument described in this specification. All questions concerning the scope of the invention are to be answered by reference to the appended claims.